1. Field of the Disclosure
The disclosure relates generally to water-soluble structures such as films. More particularly, the disclosure relates to water soluble-films which are soluble only in particular pH ranges, which find utility in the packaging of cleaning actives, such as rinse additives.
2. Brief Description of Related Technology
Water-soluble polymeric films are known in the art and are described in several references. Such polymeric films are commonly used in packaging materials to simplify dispersing, pouring, dissolving, and dosing a material to be delivered. Water-soluble film packages of such polymeric materials can be directly added to a mixing vessel, advantageously avoiding contact with toxic or messy materials, and allowing accurate formulation in the mixing vessel. Soluble pre-measured polymeric film pouches aid convenience of consumer use in a variety of applications, particularly those involving wash additives. As used hereinafter, rinse additive refers to those materials which are intended for use, or are most efficacious in a rinse portion of a wash cycle and are intended to improve a property, such as the aesthetics, feel, appearance, sanitation or cleanliness of fabrics or wares which can be washed in machine washing apparatus. Such wash additives are preferably rinse-added after an alkaline detergent wash has occurred, and include but are not limited to fabric softeners, brighteners, anti-redeposition agents, bleaches, and surfactant rinse aids for dishwashing. It is desirable to effectuate the release of the additives during the rinse portion, rather than during the wash portion, of the wash cycle. It is further desirable to add these products to a washing machine initially, at the start of the wash cycle, thereby avoiding the need to monitor the cleaning process and introduce the additives at the beginning of the rinse portion of the wash cycle. Polymeric films used to contain such additives would have to be insoluble during the wash phase and become soluble during the rinse phase, and solubility preferably is triggered by a difference in pH of the wash solution.